feat: scope passkey slots to proven owners

src/lnurlcash/passkeyOwnership.ts

@@ -0,0 +1,15 @@
+// Legacy passkey slots may be adopted only after another unlock path has
+// proven and stamped the saved wallet owner. The linking key is checked
+// against that marker before markerless slots are changed under the lock.
+
+import {linkingPubKeyHex, savedKeyOwnerId} from './keys'
+import {adoptLegacyPasskeySlots, PASSKEY_SLOTS_STORAGE_KEY} from './storage/passkeySlots'
+import {withStorageLock} from './storageLock'
+
+export const migrateLegacyPasskeySlots = async (linkingKey: Uint8Array): Promise<number> => {
+  const ownerId = savedKeyOwnerId()
+  if (ownerId === null || linkingPubKeyHex(linkingKey) !== ownerId) {
+    throw new Error('Legacy passkey migration requires a proven owner.')
+  }
+  return withStorageLock(PASSKEY_SLOTS_STORAGE_KEY, () => adoptLegacyPasskeySlots(ownerId))
+}